Heat-resisting stencil film



May zo, 1941. J, s. MAR'R'AN 2,242,313

HEAT-RESISTING STENCIL FILM Filed March 7, 1940 INVENTOR 'ATTORNEYPatented May 20, 1941 l 2,242,313 nEAT-aEsrs'nNG srENcn. MLM

John S. Marran, Stamford, Conn., assigner to L. C. Smith & CoronaTypewriters, Inc., Syracuse, N. Y., a corporation oi' New YorkApplication March 7, 1940, Serial No. 322,660

6 Claims.

This invention relates to opaque stencil sheets.

especially adapted for use in projecting machines such as moving-pictureprojectors and stere-A opticons. v

Stencil sheets for use in motion-picture projectors or stereopticons aresubjected to a high degree of concentrated heat. It is necessarytherefore that the opaque coating on the sheet be heat resistant to acomparatively high degree so that the concentrated heat from theprojecting lamp shall not 'cause a deterioration, orI disintegration, ofthe opaque coating during the passage of the stencil sheet through theprojecting'machine at a normal projection speed.

One of the objects of this invention is to provide a stencil sheet withan opaque coating of such character as to be heat resistant to such adegree as to be unaffected by the heat in the proy jecting machine whilethe stencil is vpassing through the projecting machine at a normal speedof projection.

A further object of the invention is to provide a exible, opaque,heat-resistant stencil sheet having a thin, tough, 'exible, transparentbase, preferably Cellophane, coated Awith an opaque -coating of suchcharacter as to be removed or dis.. placed from the base by the pressureofthe type of a typewriting machine or by a stylus, or other instrument,without injury to the base, to thereby produce a clear, transparentcharacter through which the light from the projecting machine willreadily pass. l

A further object of the invention is to provide` terial, such as mineralblack, a non-drying oil and a vegetable wax. With this materialiscombined a heat-resisting material, preferably a metallic dust.Aluminum dust or powder gives to the coating a heat-resisting andheat-reflecting quality and prevents the heat from the projection lampaffecting the oil and Wax during the period of projection with thestencil moving through the.

projecting 'machine at anormal projection speed.

A satisfactory formula for the production of the opaque coating has beenfound to be mineral black 5%-aluminum dust or powder 34%- nondrying oil12%-vegetable wax 49%, all by weight.-

The oil and wax and mineral black are ground together under suitabletemperature conditions to thoroughly mix them and bring them to thedesired consistency. 'I'he aluminum dust or powder is then slowly andcarefully ground into the mixture until it is completely and uniformlydistributed throughout the mass, and the mixture is of uniform density.This mixture is then applied to the Cellophane lm base preferably to oneside only, by anysuitable means, preferably by a roller distributor, andthe film base with the coating l applied is then dried.

The proportions of the ingredients may be varied within reasonablelimits without materially affecting the heat-resisting qualities of thestencil sheet. It has been found, however, that a small percentage ofmineral black or equivalent opaque v material is entirely satisfactoryfor the stencil,

adhering portion of the heat-resisting metallicA powder serving inthenature of a light lter to soften the projected light and to on theprojection screen.

In the drawing,

Fig. 1 is a view of a portion of a stencil sheet showing charactersprinted thereon;

Fig. 2 is a sectional view on the ,line 2-2 of Fig. 1; and

Fig. 31s an enlarged sectional of the stencil sheet. The base I of thestencil may be any suitable form of thin,-exible, tough, non-absorbentand transparent material. The commercial product known as Cellophanehas. been found to be practical and satisfactory. The opaque coating 2may be formed by combiningl any form ofopaquema Aprevent glaresheet whencombined with aluminum powder.

A stencil sheet produced as described may be passed through atypewriting machine and typed upon in the usual manner, the type beingbrought into contact with the uncoated side ofthe Cellophane sheet. Thelm, when placed in a. typewriting machine, is backed by a sheet ofcomparatively soft paper, placed over the coated side, and the opaquecoating is driven of by a single stroke ofthe type and adheres to thepaper.

thereby producing a clear outline of the typed character on the stencilbase or nlm.

The adhesion of the opaque coating to the lm must be such that anyportion of the coating 'may be mechanically removed by writing thereonwith a typewriting machine, or a stylus orfother pres- 4sure instrument,thereby forming transparent or translucent characters by exposing the lmbase and contrasting it with the opaquecoating surrounding thecharacters typed on the lm. It is `desirable that the degree of adhesionof tlie opaque coating to the film besuch that practically all of thecoating will be removed from the nlm by a single stroke or pressureimpression of a type. Aluminum powder contributes materially toproducing a coating which may be driven oil the nlm base freely andsharply by a single stroke of the type of a typewriting machine, leavingthe transparent nlm clean of opaque material and the impression sharp.

A small amount of the aluminum powder will adhere to the base nlm after'theopaque coating has been driven off the type.` This remaining smallportion of the powder will serve in the nature of a filter slightlyobstructing the passage of the light from the projecting machine andthereby preventing a glaring effect on the projection screen.

Bronze powder has also been found to be satisfactory as a heat resistingmaterial. 'I'he bronze power is mixed with the other ingredients inabout the same proportion as the aluminum dust or powder, namelyapproximately 34% byweight.

What I claim is:

l. A heat-resisting stencil film comprising a thin, tough, flexible,transparent Cellophane base, and a coating including mineral black 5%, anondrying oil 12%, a vegetable wax 49% and aluminum powder 34%, all byweight.

2. A heat-resisting stencil lm comprising a thin, tough, flexible,transparent Cellophane base, and a coating including mineral black 5%,

a non-drying oil 12%, a vegetable wax 49% and metallic powder 34%, allby weight.

`3. A heat-resisting stencil -lm comprising a thin, tough, ilexible,transparent Cellophane base, and a coating including mineral black, anondrying oil, a vegetable wax and aluminum powby weight, of aluminum byder, the proportion, powder greatly exceeding the proportion, weight, ofmineral black.

4. A heat-resisting stencil lm comprising a powder, .the aluminum powderconstituting ap-y proximately 34%, -by weight, of the coating.

6. A heat-resisting stencil lm comprising a thin,l tough, flexible,non-absorbent, transparent base, and a coating including mineral black,a non-drying oil, a vegetable wax and aluminum powder, the proportion ofaluminum powder, by weight, greatly exceeding the proportion, by weight,of mineral black.

JOHN S. M ARRAN.

